1. Field of the Invention
The present invention concerns a method for manufacturing a shrink-on cap, comprising the following steps:
a) prepare a heat-shrink tubing section having an opening at each of its two ends; and PA1 b) press the heat-shrink tubing section together at its one end and produce a welded or pressed seam, constituting a rim, in order to close off the corresponding opening, the rim lying substantially in a plane of symmetry of the heat-shrink tubing section. PA1 c) deform the rim so that its sharp edge and pointed corners are removed from the plane of symmetry. PA1 a) produce the new shrink-on cap; PA1 b) slide the shrink-on cap, with its open end, onto the component so that its external terminals project out of the shrink-on cap; and PA1 c) shrink the shrink-on cap onto the component by using hot air.
The invention further concerns a shrink-on cap manufactured according to the method, an electrical component protected by the shrink-on cap, and a method for protecting said component.
2. Related Prior Art
Shrink-on caps of this kind are kept on hand as bulk goods and are slid onto electrical components to be protected, for example temperature-dependent switches, and then shrunk on with the use of hot air so as to create a casing which protects the component from dirt, moisture, and electrical contact with other components. The connecting elements of the component, which are often configured as connecting leads, then still project out from said casing.
Shrink-on caps of this kind are manufactured by first cutting heat-shrink tubing sections to length, which are then preshaped and heated at their one end sufficiently that as a result of the application of two welding punches, which occurs at that end from two opposite sides, a rim closed off by a welded or pressed seam is formed. Said rim can have twice the wall thickness of the usual heat-shrink tubing, so that it is very stiff and rigid. It has a sharp edge and two pointed corners. The sharp edge and the pointed corners are retained when prefabricated shrink-on caps of this kind are shrunk onto components being protected.
In the assembly of components with the shrink-on caps and in the further processing of components encased in this fashion, many process steps are done by hand; the persons performing these process steps must perform extremely delicate operations, so that they cannot wear protective gloves.
Because of the sharp edges and pointed corners present on the shrink-on caps, injuries often occur to these persons when handling the shrink-on caps, which of course constitutes a major disadvantage.
In order to avoid these injuries, the persons therefore grasp the encased components not by the shrink-on cap but by the connecting leads, although the result of this during the further handling operations that are necessary is that the connection between the lead and the encased component is weakened or in deed completely destroyed, so that the device produced from such components often functions improperly.
In particular when the components are temperature-dependent switches which are intended to protect, for example, a coil from overheating, the switches encased in this fashion are brought directly into contact with the coil of, for example, electric motors. The switches are electrically connected in series with the coil and interrupt the electrical circuit if the temperature of the coil exceeds a predefined value. For this purpose, a bimetallic switching mechanism is arranged, in known fashion, in the interior of the switch.
To ensure that this protective function can be performed reliably, the switches must be arranged in the interior of the coil or at least must be brought very close to the coil. It has now been found, however, that these actions often result in the coil wire being damaged by the sharp edge and/or the pointed corners, which can result in malfunctions of the device constructed therewith.
The damage caused directly or indirectly by the pointed corners and sharp edges, not only to the component leads but also to other components, is particularly disadvantageous because such damage is often not at all apparent during final inspection, but instead does not become perceptible until the device in question is used.